A 25-year-old nulligravid woman presents to clinic complaining of abnormal vaginal discharge and vaginal pruritis. The patient's past medical history is unremarkable, and she does not take any medications. She is sexually active with 3 male partners and does not use condoms. Pelvic examination is notable for a thick, odorless, white discharge. There is marked erythema and edema of the vulva. Vaginal pH is normal. Microscopic viewing of the discharge shows pseudohyphae and white blood cells. Which of the following is the best next step in treatment?